I have and will be spending weeks of preparation work. Of course the locations are not truly abandoned just vacant at the time, I will be willing to pay if the location proves well on a monthly basis or a portion of the property taxes they pay. Also getting covered with insurance doesn't hurt as well, so that will be a must. The zombies in this event will be paid staff and the players need not to play zombies unless they desire. I just need ideas on locations within Ontario that would allow such an events.

You will need the following just to get started.

1) Full insurance for the property, this requires the property owner for a green light.
Policy minimum would need to be 1 million general liability coverage or more for any insurance company to touch it, not to mention insurance specifically for "airsoft" which is not common, so start hunting now. This is not cheap, so start getting ready to put away thousands to cover your overhead.

2) If any by-laws are present (and rest assured, they will be). You may be boned regardless.

3) Local authorities need to sign off on your activity. This typically requires a proposal + inspection of the property.

4) Township or the City requires a proposal and inspection of the property, they will determine if you need to apply for any permits for the event.

5) Emergency services such as Fire need to be made aware of what you are doing.